Roof systems for new buildings

When it comes to the between-rafter insulation, only the spaces between the rafters are insulated. In this context, it is advisable to attach a roofing membrane directly from the outside to the thermal insulation and above the rafters. This membrane is appropriate as underlay membrane as well and offers protection against moisture to the thermal insulation from the outside. On the inside part of the roof, i.e. on the room side, an air and vapour barrier is installed directly on the thermal insulation and on the underside of the rafters so to offer protection to the thermal insulation from moisture penetration by water vapour escaping from the room air.

In this context, the hard sheathing is attached directly to the insulation positioned between the rafters and their top. Hard sheathings are flat components, mostly made of solid wood. They are mainly used as a base for sub-roofs or under-roofing. On the one hand, they help to meet the high and still increasing legal requirements for thermal insulation, and on the other hand, they offer additional protection for the roof structure, in particular for its thermal insulation. After that, a roofing membrane is laid directly on the hard sheathing. This ensures that the thermal insulation remains permanently dry from the outside. Just like a roof without hard sheathing, an air and vapour barrier will be installed on the underside of the rafters on the room side so to offer the ideal protection for the thermal insulation from the inside from room humidity.

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The combined over-rafter and between-rafter insulation is used when the first insulation level between the rafters does not suffice to achieve the desired insulation values. In this case, an additional insulation layer, the so-called over-rafter insulation, will be laid on the rafters. Together with the traditional insulation reaching a thickness of 140 mm between the rafters, this results in an insulation thickness meeting the high legal requirements when it comes to the long-term thermal insulation. In this case, this can already be achieved with thin on-roof insulation panels so to maintain a relatively low roof structure. This optimised insulation helps to save expensive heating energy during the winter months while in summer it offers a high level of summer heat protection as well as extremely effective noise protection. An air and vapour barrier is applied to the roof inside on the underside of the rafters in order to protect the thermal insulation from room humidity.

With the pure over-rafter insulation, the whole insulation surface is installed over the rafters from the outside, even without considering possible spaces between the single rafters. If the roof is not equipped with a hard sheathing, an air and vapour barrier is first attached to the top of the rafters. The individual on-roof insulation components made of high-performance insulation materials will be positioned directly on top of it. The full-surface installation eliminates thermal bridges in the area of the rafters. In addition, the height of the rafter must just be dimensioned according to static requirements.

With the pure above-rafter insulation, the insulation will be laid over the whole surface of the rafters. The evenly thick, homogeneous insulation layer positioned over the rafters prevents thermal bridges. Consequently, your roof will be provided with seamless thermal, heat and sound insulation. A positive side effect is that the rafters only have to meet structural requirements. A roof equipped with hard sheathing can represent a real advantage if you want to make heavily structured roof areas windproof from the outside. In this context, a roofing membrane with the necessary vapour barrier layer will be laid on the top of the hard sheathing. After that, the individual on-roof insulation components made of high-performance insulation materials are positioned directly on top.